Question

A 90% acid solution is mixed with a 97% acid solution to obtain 21 liters of a 95% solution.
find the quantity of each of the solutions to get the resultant mixture
[hint. let x liters of 90% solution be mixed with y litres of 97% acid solution.
then,x+y=21 and 90% of x +97% of y=95%of 21]

Answer 1

Let  x ltr of 90% be added to (21-x) ltr of 97% acid solution.
x×90/100+(21-x)97/100=21×95/100
⇒90x+2037-97x=1995
⇒7x=42
⇒x=6
6 ltr of 90% solution is mixed with 15 ltr of 97% solution.

Answer 2

let x litre of 90% be added to(21-x)litre of 97% acidic solution
90x+2037-97x=1995
-7x=-42
7x=42
x=42/7
x=6
6 litre of 90%solution is mixed with of 97% solution